Imagine a 30-year mortgage on which you only pay2.8 percent in interest a year..Such a mortgage could already exist, but something in the banking system is holding it back. And right now, few agree on what that "something" is.

Getting to the bottom of this enigma could help determine whether mortgage lenders are dysfunctional, greedy or simply trying to do their job in a sensible way.

.Right now, borrowers are paying around 3.55 percent for a 30-yearfixed rate mortgage that qualifies for a government guarantee of repayment.That's down from 4.1 percent a year ago, and 5.06percentthree yearsago.

.Mortgage rates have declined as the Federal Reserve has boughttrillions of dollars of bonds, a policy that aims to stimulate the economy.Last week, the Fed said it would make new purchases, focusing on bonds backed by mortgages.

.The big question is whether those purchases lead to even lower mortgage rates, as the Fed chairman, Ben S. Bernanke, hopes..But mortgage rates may not declinesubstantially from here.Something weird has happened. Pricing in the mortgage market appears to have gotten stuck. This can beseen in a crucial mortgage metric.

Banks make mortgages, but since the 2008 crisis, they have sold most of them into the bond market, attaching a government guarantee of repayment in the process.

The metric effectively encapsulates the size of the gain that banksmake on those sales. In September 2011, banks were making mortgages with an interest rate of 4.1 percent. They were then selling those mortgages into the market in bonds that were trading with an interest rate, or yield, of 3.36 percent, according to a Bloomberg index.

The metric captures the difference between the bond and mortgage rates; in this case it was 0.74 percentage points. The bigger the "spread," the bigger the financial gain for the banks selling the mortgages. That 0.74 percentage point "spread" was close to the 0.77 percentage pointaverage since the end of 2007. Banks were taking roughly the same cut on the sales as they were in previous years.

But something strange has happened over the last12 months.That spread has widened significantly, and is now more than 1.4 percentage points. The cause: bond yields have fallen a lot more than the mortgage rates banks are charging borrowers.

.Put another way, the banks aren't fully passing on the low rates in the bond market to borrowers.Instead, they are taking bigger gains, and increasing the size of their cut.

So where might mortgage rates be if the old spread were maintained?At 2.83 percent - that's the current bond yield plus the 0.75 percentage pointspread that existed a year ago.

.It's important to examine why the tight relationship between bond yields and mortgage rates becomes unglued.

.Oneexplanation, mentioned in a Financial Times story on Sunday, is that the banks are overwhelmed by the demand for new mortgages and their pipeline has become backlogged.When demand outstripssupply for a product, it's less likely that its price -- in this case, the mortgage's interest rate -- will fall. There are in fact different versions of this theory..Oneholds that bank mortgage operations are still poorly run, andtherefore it's no surprise they can't handle an inundation of new applications. Another says banks deliberately keep rates from falling further as a way of controlling the flow of mortgage applications into their pipeline.If mortgages were offered at 2.8 percent, they wouldn't be able to handle the business, so they ration through price, according to this theory.

Another backlog camp likes to point the finger at Fannie Mae and Freddie Mac, the government-controlled entities that actually guarantee the mortgages.The theory is that these two are demanding that borrowers fulfilloverly strict conditions to get mortgages. Banks fear that if they don't ensure compliance with these requirements, they'll have to take mortgages back once they've sold them, a move that can saddle them with losses.

As a result, the banks have every incentive to slow things down to make sure mortgages are in full compliance, which can add to the backlog.Once this so-called put-back threat is decreased, or the banks get better at meeting requirements, supply should ease.But there is a weakness to the backlog theories.

.The banks have handled two huge waves of mortgage refinancing since the 2008 financial crisis.During those, the spread between mortgage and bond rates did increase. But not anywhere near as much as it has recently. And the spread has stayed wide for much longer this time around.

.For instance, $1.84 trillion of mortgages were originated in 2009, a big year for refinancing, according to data from Inside Mortgage Finance, a trade publication.In that year, the average spread between bonds and loans was 0.89 percentage points.And the banking sector was in a far worse state, which would in theory make the backlog problem worse.

.Today, the sector is in better shape, with more mortgage lendersback on their feet.But the spread between loans and bonds is considerably wider. In the last 12 months, when mortgage origination has been close to 2009 levels, it has averaged1.1 percentage points. This suggests that it's more than just a backlog problem..Some mortgage banks seem to be having little trouble adapting to the higher demand.U.S. Bancorp originated $21.7 billion of mortgages in the second quarter of this year, 168 percentmore than in the second quarter of last year.

Wells Fargo is currently the nation's biggest mortgage lender, originating 31 percent of all mortgages in the 12 months through the end of June.In a conference call with analysts in July, the bank's executives seemed unfazed about the challenge of meetingmounting customer demand.."We've ramped up our team members in mortgage to be able to move the pipeline through as quickly as possible," said Timothy J. Sloan, Wells Fargo's chief financial officer.He also said that the bank had increased its full time employees in consumer real estate by 19 percent in the prior12 months. Not exactly the picture of a bank struggling to expand capacity. .But if banks are readily adding capacity, why aren't mortgage rates falling further, closing the spread between bond yields?Perhaps a new equilibrium has descended on the market that favors the banks' bottom lines..The drop in rates draws in many more borrowers.The banks add more origination capacity, but not quite enough to bring the spread between bonds and loans back to its recent average..The banks don't care because mortgage revenue is ballooning.But it all means that the 2.8 percentmortgage may never materialize.

If you know the other and know yourself, you need not fear the result of a hundred battles.

Sun Tzu

We are travelers on a cosmic journey, stardust, swirling and dancing in the eddies and whirlpools of infinity. Life is eternal. We have stopped for a moment to encounter each other, to meet, to love, to share.This is a precious moment. It is a little parenthesis in eternity.